Only 43% of nurses in a survey felt they could raise concerns without thinking twice. Photograph: Darren Staples/Reuters

A whistleblowers' hotline is being set up today by the Royal College of Nursing after evidence emerged that its members are being victimised for voicing worries about unsafe practices on NHS wards.

A survey of more than 5,000 nurses found 78% feared personal reprisals or a negative effect on their career if they reported concerns to their employers. It also found that 21% had been discouraged or told not to report concerns about what was going on in their workplace.

The confidence of nurses was shaken last month when the Nursing and Midwifery Council, their regulator, struck Margaret Haywood off the professional register for exposing poor care in a film for the BBC programme Panorama. Her attempt to reveal the substandard care experienced by her patients was interpreted as an intrusion into their privacy.

The RCN will respond today by setting up a dedicated line to allow members to talk in confidence about "serious and immediate worries that patient safety is being put at risk in their workplace".

The union said it would use the information to help the nurses raise concerns and, if needed, to step in swiftly to investigate problems directly with the employers.

The move came as nurses assembled for the RCN's annual conference in Harrogate. The general secretary, Peter Carter, said the Healthcare Commission last month exposed a scandal of what it described as "appalling" care for patients admitted in an emergency to Stafford hospital.

Carter said: "This shows us what can happen if genuine concerns are dismissed or not investigated properly. We know that incident reports filled in by nurses were not acted upon, with disastrous consequences. We also know that nurses have genuine concerns that they will be victimised if they speak up. And too often they are right."

The survey found only 46% of nurses felt confident that their employer would protect them if they spoke up. Fear of reprisals left only 43% saying they would be confident to report concerns without thinking twice. In spite of these fears, 63% of nurses said they had reported concerns. About half had filled in incident forms, a formal mechanism for documenting situations that are a threat to patient safety. But only 29% said their employer took immediate action. The RCN noted: "Worryingly, more than a third (35%) said no action was ever taken."

One unnamed nurse told the union: "I have been deeply affected in a negative way for blowing the whistle. The only redeeming feature of my involvement is that eventually my efforts really did make a difference to patient care in my trust.Unfortunately there are some managers who still marginalise me and make it clear that I am persona non grata. Nurses who have witnessed how I have been treated for representing colleagues frequently tell me it is a huge deterrent for them in raising concerns."

The RCN said all trusts should hold a register of staff concerns. Carter added: "If trusts want to avoid another [scandal], they need to make every nurse aware of the protection the law gives them when they raise concerns about patient safety."

The RCN's evidence of victimisation came from an online survey of 5,428 nurses on the union's website during the last week of April. The whistleblowers' hotline number is 0845 7726 300.